IC MULTI CONFIG ADJ 3A TO-263-5

LM2585SX-ADJ/NOPB

Manufacturer Part NumberLM2585SX-ADJ/NOPB
DescriptionIC MULTI CONFIG ADJ 3A TO-263-5
ManufacturerNational Semiconductor
SeriesSIMPLE SWITCHER®
TypeStep-Up (Boost), Flyback, Forward Converter
LM2585SX-ADJ/NOPB datasheet
 


Specifications of LM2585SX-ADJ/NOPB

Internal Switch(s)YesSynchronous RectifierNo
Number Of Outputs1Voltage - OutputAdjustable
Current - Output3AFrequency - Switching100kHz
Voltage - Input4 ~ 40 VOperating Temperature-40°C ~ 125°C
Mounting TypeSurface MountPackage / CaseD²Pak, TO-263 (5 leads + tab)
Primary Input Voltage40VNo. Of Outputs1
Output Voltage12.6VOutput Current3A
No. Of Pins5Operating Temperature Range-40°C To +125°C
Filter TerminalsSMDInput Voltage Primary Max40V
Rohs CompliantYesFor Use With551011367-061 - BOARD WEBENCH LM2577,LM2585/87
Lead Free Status / RoHS StatusLead free / RoHS CompliantPower - Output-
Other names*LM2585SX-ADJ
*LM2585SX-ADJ/NOPB
LM2585SX-ADJ
  
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Page 21
22
Page 22
23
Page 23
24
Page 24
25
Page 25
26
Page 26
27
Page 27
28
Page 28
Page 22/28

Download datasheet (2Mb)Embed
PrevNext
Application Hints
PROGRAMMING OUTPUT VOLTAGE
(SELECTING R
AND R
)
1
2
Referring to the adjustable regulator in
voltage is programmed by the resistors R
lowing formula:
V
= V
(1 + R
/R
)
OUT
REF
1
2
Resistors R
and R
divide the output voltage down so that it
1
2
can be compared with the 1.23V internal reference. With R
between 1k and 5k, R
is:
1
R
= R
(V
/V
− 1)
1
2
OUT
REF
For best temperature coefficient and stability with time, use
1% metal film resistors.
SHORT CIRCUIT CONDITION
Due to the inherent nature of boost regulators, when the out-
put is shorted (see
Figure
38), current flows directly from the
www.national.com
FIGURE 38. Boost Regulator
input, through the inductor and the diode, to the output, by-
passing the switch. The current limit of the switch does not
limit the output current for the entire circuit. To protect the load
Figure
38, the output
and prevent damage to the switch, the current must be ex-
and R
by the fol-
1
2
ternally limited, either by the input supply or at the output with
an external current limit circuit. The external limit should be
where V
= 1.23V
REF
set to the maximum switch current of the device, which is 3A.
In a flyback regulator application
dard transformers, the LM2585 will survive a short circuit to
2
the main output. When the output voltage drops to 80% of its
nominal value, the frequency will drop to 25 kHz. With a lower
where V
= 1.23V
REF
frequency, off times are larger. With the longer off times, the
transformer can release all of its stored energy before the
switch turns back on. Hence, the switch turns on initially with
zero current at its collector. In this condition, the switch current
limit will limit the peak current, saving the device.
FIGURE 39. Flyback Regulator
22
1251555
(Figure
39), using the stan-
1251556